I. A. Izmailov

National Academy of Sciences of Ukraine | ISP · Institute of Semiconductor Physics - Department of Theoretical Physics

ZnO is one of the best photoactive wide-gap metal-oxide semiconductor materials, whose optical and electronic properties are of great interest for modern nanophotonics and quantum electronics [1,2]. In particular, photoexcited ZnO exhibits excitonic photoluminescence (PL) in the near UV spectral range even at room temperature (RT). But despite adva...

Low-temperature air plasmas in dielectric barrier discharges (DBD) are of great interest for science and practice, e.g., in materials processing [1,2]. But despite the advances in DBD plasma physics, the non-equilibrium kinetics of DBD plasma chemistry in humid air is not very clear, especially regarding metastable electronically excited states (ME...

Extreme UV plasma sources including UV excimer lasers and excilamps are of great interest for modern science and technology, for instance, in nanolithography [1,2]. But despite the advances in excimer plasma physics, non-equilibrium kinetics of excimer plasma is still not entirely clear, in particular, regarding metastable excited species (MES). We...

Non-equilibrium plasma in high-voltage gas discharges of the so-called apokamp type (blue jets, red sprites) is of great interest for science and practice [1]. But, despite the advances in apokamp plasma physics, the mechanism of apokamp plasma chemistry is not very clear, in particular, concerning electronically excited reactive oxygen and nitroge...

Kinetics of non-equilibrium plasma in dielectric barrier discharges (DBD) is of great interest for science and practice [1]. But despite the advances in plasma physics, the mechanisms of plasma-chemical processes are not very clear, in particular, concerning electronically excited states (EES) of oxygen and nitrogen atoms and molecules. We tried to...

Plasma enhanced oxidizing and nitriding processes are of great interest for physics and applications. However, despite all advances in plasma technology, mechanisms of non-equilibrium plasma chemistry are not quite clear, particularly concerning reactive oxygen and nitrogen species (ROS/RNS) in metastable states. We tried to study this matter more...

In a nonequlibrium plasma of a gas-discharge HgBr lamp, the terminal electronic state of the HgBr(B–X) radiative transition with a peak wavelength of 502 nm remains populated for a relatively long time and is repeatedly excited to the upper state in collisions with plasma electrons. This transfer of the HgBr molecules from the ground state X to the...

The effects of electronically excited reactive oxygen (ROS) and nitrogen (RNS) species in metastable states O2*(a,b), N2*(A) and other small but important radicals in the kinetics of non-equilibrium plasma-enhanced oxidation and nitriding are studied and analyzed in experiments and numerical simulations.

A kinetic model of the working medium of a gas-discharge excilamp on the B–X transition of mercury bromide, HgBr, excimer molecules has been proposed. The model explains the non-monotonic dependence of the excilamp radiation intensity on the partial pressure of mercury dibromide, HgBr2, molecules by the attachment of electrons to these molecules. H...

Key kinetic processes that occur in reactive heterophase plasma during fast adiabatic expansion and cooling of the lead azide detonation products in a supersonic flow including nonequilibrium radiation, vapor condensation, atomic clastering, and light scattering have been studied and analyzed in order to interpret the experiments in the lead-azide...

The kinetics of the superluminescence of lead atoms, Pb 3P 10 → 1D2 (722.9 nm) and 3P10 → 3P2 (405.8 nm), at the fast adiabatic expansion and cooling of the detonation products of lead azide Pb(N3)2 in vacuum has been studied. The effects of the condensation and scattering of light from drop clusters in an optically active heterophase medium has be...

The effects of lasing in two-phase gas-dispersed media containing fine metal droplets under conditions of photon-stimulated chain-branched reactions of oxidation are kinetically modeled and analyzed.

To look forward to new trends in modern gas lasers and their applations, the current theoretical and experimental studies (state-of-art) on search of new active media for high-power short-wavelength gasdynamic and chemical lasers are reviewed. The basic physical aspects (optical, kinetical, thermal and fluid dynamical) in operation of gas flow las...

The effects of lasing in two-phase dispersed lead azide plasma detonation products following by cluster condensation and light scattering are kinetically modeled and analyzed.

Kinetics of nonequilibrium emission radiation following the detonation of lead azide and light scattering at the condensation of the products in supersonic expanding flows are explored for interpretation of experiments in active media of detonation plasmodynamic lasers.

Peculiarities of kinetics of radiative and collisional relaxation of excimer molecules in excimer plasma of high density is analyzed for better understanding of physics of processes and interpretation of experimental data in active media of excimer lasers and exilamps.

Peculiarities of kinetics of electronic-vibration relaxation of excimer molecules in gas-discharge plasma is analyzed and its influence on radiation characteristics of pulsed-periodic mercury-monohalide excilamps is determined. A novel theoretical model for description of mechanism of formation of HgBr(Cl) excimer molecules is applied, and a good a...

Peculiarities of kinetics of electronic-vibrational relaxation in the work media of gas-discharge pulsed-periodic mercury-halide excilamps is analyzed, novel improved model for description of mechanism of formation of HgBr(Cl) excimer molecules is applied, and good adequate interpretation of experiments on non-stationary luminescence in HgBr2(Cl2):...

Spectral and kinetic peculiarities of the luminescence of electronically excited short-lived two- and three-atomic molecular complexes of halogens and halides of noble gases in partially ionized chemically active plasma are analyzed and discussed.

An overview of optical effects in micrometer-sized droplets is presented. The fundamentals of microdroplet optics are expounded. The scope of the analyzed phenomena includes enhancement of the spontaneous emission probability, laser generation, Raman light scattering, changes in the rates of physicochemical processes, and peculiarities of action on...

Effect of free electrons on kinetics of radiative relaxation of excimer molecules in excimer plasma of high density is analyzed for better understanding of physics of processes and interpretation of experiments in active media of excimer lasers and exilamps.

Nonequilibrium vibrational relaxation of excimer molecules is analyzed for better understanding of physics of processes and interpretation of experiments in excimer plasma of high density.

Kinetics of vibrational relaxation of excimer molecules in collisions with electrons is analyzed for better understanding of physics of processes and interpretation of experiments in excimer plasma.

Effects of electrons in relaxation kinetics of excimer molecules are analyzed for better understanding of physics of processes and interpretation of experiments in nonequilibrium excimer plasma.

A review of the vibrational relaxation of excimers is presented. Various kinetic models used in the literature to interpret experimental data and to model excimer lasers are discussed. Of these, those based on the Fokker–Planck diffusion equation are the most general due to the essentially nonequilibrium population of the hundreds of high vibration...

To look forward to new trends in modern gas lasers and their applations, the current theoretical and experimental studies (state-of-art) on search of new active media for high-power short-wavelength gasdynamic and chemical lasers are reviewed. The basic physical aspects (optical, kinetical, thermal and fluid dynamical) in operation of gas flow las...

To state more precisely our knowledge of the vibrational energy transfer with Cl2 molecules in active media of the gas flow and chemical lasers, the nonequilibrium vibrational relaxation of the thermally heated and partially dissociated molecular chlorine in the supersonic flow is studied. Using experimental technique based on the sensitive spectro...

Results of experimental and theoretical studies of kinetics and mechanism of the fast V-T relaxation of excited Cl2 molecules by recombining Cl atoms in supersonic gas flow and chemical laser active media are presented and analyzed.

A new concept of solar powered laser is proposed for direct transformation of solar light into laser energy with using the open solitary dielectric waveguide (optical fiber) placed into the active medium containing the photoexcited singlet oxygen metastable molecules O2(a1).

The luminescence of dispersed media during light generation in spherical microresonators has been investigated theoretically. The effect that is predicted for the first time to our knowledge is a drastic increase of the dispersed-medium luminescence intensity in the case of an inverted population of the metastable-molecule energy levels.

Review of pre-laser studies presented indicates principal possibilities to create a new class of thermally and chemically driven molecular gas dynamic lasers on electronic transitions in visible and near IR diapasons on the base of S+S, Cl+Cl, Br+Br and other halogens radiative recombination pumping. © 1993 ICTP.

Based on the measurements of the absolute emissivity of the thermally heated molecular chlorine in the shock wave flow, the redetermination of radiative characteristics of the Cl2 B3(Pi)o+u yields X1(Sigma)+g and A1(Pi)1u yields X1(Sigma)+g electronic transitions was made with the aim of pre-laser studying a potential new laser active media. Reason...

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The stimulated-emission quantum yield of an electronically excited molecule is analyzed as a function of the vibrational relaxation time. Optical gain saturation and a finite lifetime of the lower laser level are taken into account. Use of the theoretical model is illustrated in the example of optimizing the parameters of a XeF laser. The method us...

The dependence of the quantum yield of induced molecule stimulated emission from molecules in the excited electron state on the time of vibrational relaxation is studied taking into account gain saturation in the case of the finite lifetime of the laser lower level. A theoretical model of the vibrational relaxation of electron-excited molecules in...

This paper presents a theoretical investigation of the luminescence of a weakly amplifying medium with a disperse condensed phase when lasing occurs in spherical particles acting as microcavities. It is predicted that the disperse medium will exhibit anomalous luminescence when population inversion occurs on the levels of metastable molecules. The...

The time kinetics of the vibrational relaxation of excimers is studied in the diffusional approximation. Simple formulae for functions of nonstationary vibrational distribution are found for the electronically excited molecules. Some spectral-kinetic dependencies of the excimer luminescence are explained in a new way. The possibilities of the deter...

Based on the measurements of the absolute emissivity of the thermally heated molecular chlorine in the shock wave flow, the redetermination of radiative characteristics of the Cl2 B3(Pi)o+u yields X1(Sigma)+g and A1(Pi)1 yields X1(Sigma)+g electronic transitions was made with the aim of pre-laser studying a potential new laser active media. Reasons...

In the report, current theoretical and experimental studies on development of a new molecular electronic transition gas flow lasers on the base of S+S, Cl+Cl, Br+Br radiative recombination reactions are reviewed.

A theoretical analysis is made of the kinetics of inverted population of SO2 levels in a mixture containing vibrationally excited oxygen O2(X, v), formed as a result of relaxation of the [MATH] electronic energy. It is shown that the gain for the SO2 transitions at the 12 and 16 µm wavelengths is sufficient to achieve lasing.

There are predicted 1) the existence of the far IR optical activity of the heteronuclear excimer molecules (EM'S) ; 2) the formation of an inverse population of certain vibrational - rotational levels of EM's ; and 3) the amplification of the IR radiation corresponding to transitions between those levels.

A gain of visible emission of excited singlet oxygen O2(a) dimers in gas media generated by a chemical singlet oxygen generator has been calculated.

A new method is proposed for direct transformation of electronic energy of metastable species in inverse medium into energy of waveguide modes localized in a dielectric waveguide. Different waveguide configurations are examined. Numerical calculations show that transformation efficiency can be as high as 15-20%.

It is theoretically predicted that the presence of a condensed disperse phase in the form of spherical droplets in an active gas media with electronically excited metastable molecules can bring an anomalous increase of their luminescence as a result of stimulated emission into whispering gallery modes of the droplets.

Results of theoretical and experimental studies on molecular electronic transition gasdynamic lasers on the base of S+S, Cl+Cl, Br+Br radiative recombination reactions in supersonic flows are analyzed and discussed.

The excimer vibrational relaxation have been studied in the diffusional approximation, and stationary substantially non-equilibrium populations of high vibrational levels have been found. New formulae have been derived for quantum yield of UV lasing. Taking into account the vibrational relaxation the new effect of far-IR radiation amplification in...

The IR activities of excimers due to transitions between different electron states are predicted. The detection of spontaneous and induced IR transitions in excimer molecules is shown to be possible in the active cross sections of excimer lasers. IR spectrum measurements can thus be used for determining spectroscopic constants.

Results of theoretical and experimental studies of a new gasdynamic chemical laser on Cl2(B-X) electronic transitions with Cl+Cl recombination pumping are presented.

A theory is derived for the luminescence of a medium with a condensed disperse phase during the excitation of light in spherical particles which serve as microresonators, It is predicted, for the first time, that there can be a significant intensification of the luminescence of a disperse medium which contains molecules with a population inversion.

The paper examines the possibility of conversion of the energy stored in an inverse medium containing excited metastable molecules or atoms to the energy of waveguide modes localized in a low-loss dielectric waveguide. The generation condition is shown to be satisfied for a certain type of localized closed waveguide modes. A waveguide array in a me...

Light generation at the whispering gallery modes in spherically excited drops is investigated theoretically. It is shown that the quality of such modes is largely determined by the radiative attenuation and scattering of light at the drop surface oscillations. Criteria of light oscillation excitation are obtained with allowance for both attenuation...

A theoretical analysis is made of the kinetics of population inversion of SO2 levels in a mixture containing vibrationally excited oxygen O2(X, ν), formed as a result of relaxation of the O2(1Δ) electronic energy. It is shown that the gain for the SO2 transitions at the 12 and 16 μm wavelengths is sufficient to achieve lasing.

The kinetics of the inverse population of levels in SO2 mixed with vibrationally excited oxygen formed as a result of O2(1 Delta) electron energy relaxation is studied. For transitions in SO2, the light gain at wavelengths of 12 and 16 microns is shown to be sufficient for obtaining laser action.

A theoretical analysis is presented of the conditions necessitating the occurrence of the partial population inversion on electronic states of diatomics as a result of the electronic energy transfer from N (A 3Sigma/+/u). It is shown that the light gain can exceed 0.0001/cm in highly diluted gas mixtures under atmospheric pressure at the N2(A) conc...

This paper analyses the conditions necessary for partial electronic state population inversion in diatomics caused by electronic energy transfer from N2(A 3Σu+). It is shown that the light gain can exceed 10^−4 cm−1 in highly diluted gas mixtures under atmospheric pressure at N2(A) concentrations close to 10^14 cm−3.

A study is made of EE-prime transfer between N2(A) and radiating molecules. Kinetic molecules describing molecule-acceptor distribution in the ground and excited electron states are discussed. Conditions are determined for the formation of inverse population at the electron-vibrational levels of electron energy acceptors. It is shown that light amp...

The paper presents the results of experimental and theoretical kinetic and spectroscopic studies of dynamics of radiative recombination of Cl atoms in incident and reflected shock waves and in supersonic flows, following by formation of inversion population of electronically excited states of chlorine molecules Cl2 (B3П(0+u),v) and stimulated emiss...

Kinetics and mechanism of radiative recombination of chlorine thermally heated and dissociated in incident and reflected shock waves and adiabatically cooled in supersonic expanding flows have been studied in the wide rage of thermodynamic parameters. Spectral-kinetic characteristics are summarized in terms of spectral and integral photorecombinati...

A new physical phenomenon - an increase in luminescence intensity of the singlet oxygen in a disperse medium (DM) as compared to that in a gas - is theoretically predicted. Two cases are considered: (1) a stationary case in which O2(1Delta) in the DM is excited at a specified rate; and (2) a nonstatinary case in which liquid drops are quickly intro...

Level population in excimer lasers based on inert gas halides is examined. The analysis presented here predicts the existence of population inversion between certain vibrational-rotational levels of excimer molecules and the amplification of the IR emission corresponding to the transitions between these levels. The discussion is illustrated by resu...

The electron-vibrational relaxation kinetics of excimer molecules in the active medium of the KrF-laser is investigated theoretically. Formulas are obtained which describe the quantum yield as a function of photon flow in the cavity, mechanisms of the formation of electron-excited molecules, and composition of the active gas medium.

A theoretical analysis is made of the kinetics of electronic-vibrational relaxation of excimer molecules in the active medium of a KrF laser. Equations are derived to describe the dependence of the lasing quantum efficiency on the photon flux in the resonator, on the mechanism of formation of electronically excited molecules, and on the composition...

Energy relaxation in an O2(1Delta)/O2/SO2 mixtures is analyzed theoretically. It is shown that light amplification for vibrational-rotational transitions of the nu3-nu2 band (lambda = 11.8 microns) of the SO2 molecule arises in this system.

The kinetic and spectroscopic study of formation of electronically excited states of chlorine molecules at recombination of chlorine atoms is presented. On the basis of measurements of emissivity and absorptivity of dissociated chlorine in incident and reflected shock waves and in supersonic flows, a theoretical model was constructed, which explain...

A model for the transfer of electron energy between metastable and emitting molecules is proposed, and conditions for the population inversion of electron-vibrational levels of acceptor molecules are established. It is shown that, in an N2(A) active medium, optical gain factors are achievable that are sufficient to obtain lasing in the visible and...

An investigation is made of the vibrational distribution of molecules in an electronically excited state subject to an allowance for the effects of the pumping, vibrational relaxation, electron quenching, and conversion to other states. Expressions for the quantum efficiency of the spontaneous luminescence and for the maximum quantum efficiency of...

The vibrational distribution of molecules in an electronically excited state is studied with consideration given to pumping, vibrational relaxation, electron quenching, and conversion into other states. Expressions for the quantum yield of the spontaneous luminescence and for the ultimate quantum efficiency of the pump conversion into laser radiati...

New physical phenomena involving an enhancement of the luminescence intensity of metastable atoms and molecules in disperse media in comparison with gas media are predicted theoretically. A method for producing an excited disperse medium is proposed which consists in the condensation of metastable atoms and molecules in a supersonic nozzle. Several...

A new physical phenomenon involving a discontinuous increase in the intensity (amplification factor) of the emission of metastable atoms and molecules under conditions of rapid condensation is predicted theoretically. The theoretical concepts developed here are applied to the calculation of the luminescence of specific metastable atoms and molecule...

Kinetics of intensive recombination radiation of Cl2 molecules thermally heated and dissociated in incident and reflected shock waves and adiabatically cooled in supersonic expanding flows have been studied using measurements of emission and absorption spectral properties and detailed modeling of physical-chemical atomic-molecular processes in none...

The excitation of lasing in a bleaching wave is studied allowing for the characteristic features of the propagation of light in a medium with variable real and imaginary parts of the permittivity. The threshold conditions for lasing are found and analyzed. The results are applied to specific optically pumped laser systems.

The excitation of a laser in a bleaching wave is studied theoretically, assuming a light propagation medium with varying real or imaginary dielectric permittivity. Threshold conditions for laser excitation are found and analyzed. The results are used to study the excitation of optically pumped Kr2F excimer lasers.

Qualitative regularities have been established for Cl+Cl intense chemiluminescence in a supersonic nozzle flow. Kinetic parameters for Cl2 electronically excited states are estimated. The conditions promising for partial population inversion on Cl2 (B-X) electronic transitions radiating in the near IR spectral region are determined.

Kinetics and mechanisms of recombination pumping of molecular states for electronic transition lasers are analyzed in theory and experiment.

The properties of a photochemical XeO excimer laser excited in a one-dimensional photobrightening wave are examined. The space-time characteristics of the laser active medium are determined, and the population-inversion criterion for the XeO molecules is considered. Also determined are the natural modes in a resonator with a one-dimensionally inhom...

In communication, it is reported on quantitative parameters of electronic kinetics of dissociating-recombining Cl2 molecules determined from the complex experimental and theoretical studies of Cl2:Ar mixtures in shock waves and supersonic flows at various temperatures and pressures by spatial-temporal optical emission and absorption spectroscopic m...

The recombination gasdynamic lasers based on S2 and Br2 is studied, and recombining flow parameters are found numerically. Conditions for population inversion are determined and light gain values are calculated taking into account the kinetics of the electron states within the S2 and Br2 molecules. The role of a gas-diluent in the GDL is briefly di...

An expression is obtained for the optical gain factor at electron transitions of diatomic molecules both for the low-pressure range (Doppler broadening) and the high-pressure range (Lorentz broadening). It is shown that for a correct determination of the gain factor it is necessary to take into account: (1) the complex structure of the emission spe...

It is proposed that a feedback resulting from scattering be used to achieve lasing in a disperse reactive medium. The example of a simple two-level system shows that under advanced lasing conditions the quantum efficiency of the radiation emission approaches the quantum efficiency of the excitation of the upper level, and the emission spectrum beco...

Radiative recombination of chlorine atoms is experimentally studied. Non-equilibrium atom concentrations are obtained by thermal dissociation of Cl2 molecules in a shock tube followed by fast cooling in a supersonic nozzle. Recombinative emission at high (above 10^17 cm−3) concentrations of Cl atoms is observed for the first time. The emission in t...

The feasibility of using radiative recombination reactions in optical-transition lasers is assessed. A classification is presented of various population types of excited states of recombination products. Methods for determining population inversion conditions and light amplification magnitudes for recombination reactions are discussed. An analysis...

The radiative channel of halogen atom recombination reactions is discussed using experimental data. It is found that various types of population of excited electronic states are formed during recombination. Calculations are made of the optical amplification cross sections for various transitions. It is found that for recombining atom concentrations...

An investigation is made of the photolysis of gaseous media accompanied by recombination reactions. It is shown that exposure of these media to high-power radiation causes complete or partial bleaching by nonsteady-state photochemical waves. High-intensity external radiation can produce high concentrations of atoms and radicals (1018–1019 cm–3) and...

A theory for the optical pumping of a molecular laser using electronic phototransitions in a dense gas of diatomic homonuclear molecules is derived. (AIP)

A theory is developed of an electronic-phototransition cw chemical laser initiated by a shock wave in a dense reagent stream. Calculations are made of the population inversion behind the shock wave front in the case of photorecombination reactions. The formation of a waveguide which localizes the lasing mode in the inversion zone is demonstrated. C...

In this paper are investigated the criteria of the thermally initiated population inversion for the system of molecular electron-vibrational levels.

A theory is developed for an electron-optical-transition chemical laser initiated by a shock wave in a dense reactant flow. The inverted population behind the shock front is calculated for the case of optical recombination reactions. It is shown that a waveguide is produced which localizes the laser's operating mode to the inversion zone. The waveg...

The theoretical analysis deals with a steady-state, shock-wave-triggered photorecombination laser employing a supersonic gas flow of atmospheric density. The population inversion and the waveguide formation which arise behind the shock front are studied for an O3-Ar and an O3-CO gas mixture. The optical gain in the waveguide modes and the specific...

The theory of optically pumped recombination lasers is examined with allowance for gas heating and gasdynamic disturbances of the medium in the cases of photolysis, parasitic chemical reactions, and gain nonuniformity. Two types of gas mixtures - (1) X2 + M and (2) AX + M - are examined, in which photolysis initiates nonequilibrium atom recombinati...